C.1 Overview

C.1.1 Scope

The Query/Retrieve Service Class defines an application-level class-of-service which facilitates the simple management of composite object instances in a manner functionally similar to ACR-NEMA 300-1988. The types of queries which are allowed are not complex. This Service Class is not intended to provide a comprehensive generalized database query mechanism such as SQL. Instead, the Query/Retrieve Service Class is focused towards basic composite object instance information queries using a small set of common Key Attributes.

In addition, the Query/Retrieve Service Class provides the ability to retrieve/transfer a well-identified set of composite object instances. The retrieve/transfer capability allows a DICOM AE to retrieve composite object instances from a remote DICOM AE or request the remote DICOM AE to initiate a transfer of composite object instances to another DICOM AE.

Note: Functional similarity to ACR-NEMA 300-1988 facilitates the migration to DICOM.

C.1.2 Conventions

The following conventions are used to define the types of keys used in Query/Retrieve Information Models.

Symbol Description
U Unique Key Attribute
R Required Key Attribute
O Optional Key Attribute

C.1.3 Query/retrieve Information Model

In order to serve as an SCP of the Query/Retrieve Service Class, a DICOM AE possesses information about the Attributes of a number of stored composite object SOP Instances. This information is organized into a well defined Query/Retrieve Information Model. The Query/Retrieve Information Model shall be a standard Query/Retrieve Information Model, as defined in this Annex of the DICOM Standard.

Queries and Retrievals are implemented against well defined Information Models. A specific SOP Class of the Query/Retrieve Service Class consists of an Information Model Definition and a DIMSE-C Service Group. In this Service Class, the Information Model plays a role similar to an Information Object Definition (IOD) of most other DICOM Service Classes.

C.1.4 Service Definition

Two peer DICOM AEs implement a SOP Class of the Query/Retrieve Service Class with one serving in the SCU role and one serving in the SCP role. SOP Classes of the Query/Retrieve Service Class are implemented using the DIMSE-C C-FIND, C-MOVE, and C-GET services as defined in PS 3.7.

Both a baseline and extended behavior is defined for the DIMSE-C C-FIND, C-MOVE, and C-GET services. Baseline behavior specifies a minimum level of conformance for all implementations to facilitate interoperability. Extended behavior enhances the baseline behavior to provide additional features which may be negotiated independently at Association establishment time.

The following descriptions of the DIMSE-C C-FIND, C-MOVE, and C-GET services provide a brief overview of the SCU/SCP semantics:

a) A C-FIND service conveys the following semantics:

Note: In this Annex, the term “Identifier” refers to the Identifier service parameter of the C-FIND, C-MOVE, or C-GET service as defined in PS 3.7.

b) A C-MOVE service conveys the following semantics:

Note: This does not imply that they use the same AE Title. See C., C. and C. for the requirements to the C-MOVE SCP conformance.

c) A C-GET service conveys the following semantics: